Setts



E. H. BRISTOL.v THERMOMETER. APPLlcAnoN FILED ocr. l. '1914.

2 Sums-SHEET x.

00- www,

Patented June 17, 1919.

E. H. BRISTOL. THERMOMETER. A APPLlcATloN FI'LED ocr. I. 1914. ,S''K Patented Junl?, 1919.

- 2 SHEETS-SHEET 2- 'and among other objects aims and indicating` y EDGAR H. BRISTOL, OF roxiaondMAssAcHusETTs, Assienon To THE roxrono COMPANY, 'OF Foxiaono, MAssAOHUsETTs, A CORPORATION oir-iiIAssAonU- "Leonesa Be it known that I, EDGAR H. BRISTOL, a

citizen of the United States, and a resident v vof' Foxboro, Massachusetts, an Improvement the following description, in

have 'invented in Thermometers, of'which connection with the accompanying drawings, is a specification, like characters on the drawings repre` senting like parts. v

This invention relates to thermometers to provide a simple and accurate thermometer for registering low temperatures. The character of the invention may be best understood by reference to the following description of an illustrative embodiment thereof lshown in the accompanying drawings, wherein:

Figure 1 is a'front'elevation of th,e illustrative thermometer shown herein as embodying the invention; and

Fig. 2 on an enlarged scale is :a view partly in side elevation and partly in section of the thermometer shown in Fig. 1.

Y Referring to the drawing, the illustrative thermometer shown f therein as embodying the invention comprises a casing 1 containing an index 3 adapted to be' moved over a dial 5 whichmay loe mounted on a plate 7 adapted to be rotated by a usual clock train (not shown). To govern the movement of the index there are provided compensating devices shown herein in the formi of coiled helical tubes 9 and 11 arrangedin tandem. To support these tubes there is provided a frame consisting of two posts 13 and 15 connecting end plates 17 vand 19 in which is journaled a shaft 21.

Y receive said posts is a ring '50 shaft 21 and-secured thereto.' Thefree end shaft and tolone end of said-tube. mit movement from the compensating tube to the shaft there :is lconnected thereto an l vsiiiiilar diagonal arm" `strip35'having .one

and the opposite end connected to a sleeve4 Intermediate said plates and apertured to secured on the back of the casing 1. One

` end of the compensating tube -9 is secured to an arm 25 vprojecting from a boss'27 fast on the ring 23. Theindica'ting tube 11 is independent frame.

Itis carried by ,and Isupported on saidl shaft 21 by an 'arm 9 connected to said armi 31l extending` 'diagonally toward the of the indicating'tube is connected by a 33-with a U-shaped end loose on said shaft 23 .conveniently of the compensating tube and thev v.To trans.

place of use.` edegreea'the u per limit for which the ther- THERMOMETER.

191i. serial No. 864,526.

37 rotative on saidl shaft and carrying the index 3 referred to.

The indicating and compensating tubes are of equal length and capacity and are filled with'alcohol or any appropriate iiuid. In order to make certainn that the tubes contain equal volumes their.` ends may be pro-v vided with short pipes 39 and 41 which may constitute extensions of said tubes. These pipes are cut off and their ends are sealed according to the lengths necessary to pro` vide said equal volumes.

The indicating tube is connected to a pipe of small gage 43 having a portion of its .length formed to present a helical coil 45 encircling the shaft 21 and conveniently located within and spaced from the compensating tube 9. The pipe is led thence to a three-way union 47 which is soldered or otherwise made fast to the post 13 of the tube supporting frame. This union is con` nected to a pipe 49 passed through the boss 27 referred to and led thence to a temperature responsive bulb 51 shown herein as a continuation of the pipe 49 and coiled in the form 'of a helix, thereby providing a bulb having an extensive surface rendering the same sensitive and quickly responsive to temperature conditions. To protect the bulb and prevent distortion thereof it may be provided with a cylindrical casing 53 per` forated to permit the free access to the bulb of the mediumthe temperature of which is to be taken.

"The coil 45 by'being interposed between the fixed union 47 and the end of the indieating coil provides a readily flexible connection for the pipe with the indicating tube which will permit free and unimpeded inove- 'ment of the indicating coil in response to temperature changes.

This thermometer may be used for registering the low temperatures of refrigerating vplants and might experience, for example, a range of temperature' from 20o-Fahrenheit below zero to 20 above zero. The latter temperature is lower than usual atmospheric Atemperatures suchas the thermometer would be likely to experience in shipmen to, its "A temperature higher than 20 moineter is esigned, wouldbelikely to create-an excessive pressure inthe system such as ,might yunwind the helical indicating tube and stretch or distort the-.same suico' 1ct f iio Y ciently to destroy its accuracy when placed' in use. To avoid any possibility of' this occurrence there is provided means for varying the effective volume of the system, thereby reducing or increasing the pressure in the system. To accomplish this a pipe 55 is provided having one end connected to the threeway union 47 referred to and its opposite end. entered in a hole in the center of a disklike thick plate 57 secured by screws to the casing. The pipe may be soldered in said hole to prevent any possibility of leakage around the same and the rear face of said plate may have a radial groove 59 to accommodate said pipe. Over the open end of said pipe is a very thin diaphragm 61 of bronze or other appropriate material having pipe and in so doing it increases the volume` its margin sweated or otherwise made fast 'to said plate. The pressure in the system will tend to cause this diaphragm to bulge upward away from the open end of said of the system and reduces the pressure therein. The movement of the diaphragm is sufficient to provide anjincreased volume Sullicient to prevent undue strain on or distortion of the instrument. To control this pressure a box 63 may be threaded to said disk plate, said box having a cylindrical` chamber receiving a pressure disk v65 adapted to be pressed toward said diaphragm by the engagement therewith of the end of a screw 67 tapped intosaid box and having a handle 69 permitting the ready turning thereof. When the screw istightened it lpresses said diaphragml down toward the 'open end of said1 pipe and reduces thevolume of and increases the pressure in the system. The construction may be so arranged that when the screw is set`down to the limit of its adjustment the appropriate pressure in the system will behad.

When the instrument is being shipped the L .i screw is adjusted to release the diaphragm and the pressure in the system thereon causes `the same to' bulge away from the open pressure'for use..

If the refrigerating plant .should be shut" ,down the screw is again released, in order to prevent injury to the instrument from y temperatures higher than the range of temperature for which the instrument is designed.

A pipe 71 `is connected to the compensatf ing tube and bulb and is similar to and of substantially equalI len th 'with the pipe which leads from the bu b to the indicating tube, but the end of the compensating tube pipe adjacent the bulb is closed and does not communicate therewith. .The temperatures surrounding the indicating and compensatto which the bulb is\subjected. IThese equal length pipes .are equally responsive to such outward temperatures and prevent the influencing of the index therefrom.

The indicating and compensating tubes asshownherein are coiled in the same direction, but their opposite ends are connected to the index and shaft respectively. Consequently pressure variations in said tubes create winding or unwinding movements thereof in opposite directions. The indicating tube is responsive both to the temperatures in the refrigerator and to temperatures external thereof, whereas the compensating tube is responsive merely to temperatures exterior thereof. Since said tubes work in opposite directions the eHect of external conditions onone will neutralize such effect on the otherA and the indicating tube will be accurately moved in response merely to the temperature Within the refrigerator and will cause the index to produce an accurate registration of such temperature.

Since the pressure within the system is appropriate for the range of low temperatures for which the instrument is designed the graduations on the scale Jmay be widely spaced, thereby permitting an easy visualization thereof and greatly facilltating the quick accuratereading of the index. Y

The operation of the instrument may be brieliy described as follows. We shall assume that the screw 67.. has been actuated to `seat the diaphragmr 61, .therefore the volume of the system including the `various pipes and the two tubes 9 and 1l is constant. The bulb comprising the coil 51 and its protective casing 53 is exposed to the temperature which it is desired to measure, the casing l Ibeing located at any convenient distance away. The coil 51 is of such form and of such material that it is not perceptibly distorted by variations of pressure caused by variations of temperature. The rugous surface presented by the coil, however, provides a large area susceptible to the'temperature conditions to be measured.

The pressure developed in the bulb coil 51 is transmitted without 'any impairment due to distortion ofthe coil through the connecting pipe 49, through union 47, to tube 11 which is distorted thereby and actuates the index 3. TheV free movement ofthe tube is permitted because of the coil 45 which prevents the pipe from exerting any drag upon the' tube. The thermal conditions about the instrument and about the transmitting connection are active on; the pipe 71 and the tube 9 itself to distort the latter and this distortion will be transmitted by the connection Slto the shaft 21 and' from this shaft to the tube 11 and only the algebraic sum of the movements of the tubes 9 and 11 will be transmitted to the index, this resulting movement being an accurate measure of the temperature conditions surrounding the bulb of the instrument.

Having described one illustrative embodiment of the invention without limiting the same thereto, what I claim as new and desiie to secure by Letters Patent is:

1 .An instrument of the class4 described comprising, in combination, an index, and governing means therefor including indicating and compensating coiled tubes, a frame, a Shaft journaled in. said frame, means for fixedly supporting one of said coiled tubes, means for connecting the saine to the shaft to communicate motion thereto, means to slipport the `other tu'be on said shaft to receive motion therefrom andv means operatively connecting said second tube to the inde-x.

2.` An instrument of the class described comprising, in combination, an index, a

, tubes, means for fixedly supporting an end of one of the tubes and means for connecting its other end to the shaft to communicate motion thereto, means to support one end of the other -tube from the shaft, means operatively connecting its other end with the index, fluid containing systems for exposure to temperature conditions comprising pipes communicating with said tubes one opening to the fixed end of the first tube and the other to the shaft-*supported end of the second tube by a flexible tubular connection 45.

3. An instrument of the class described comprising an indexand governing means 4. An instrument ofthe class described to the so-called opposite end of comprising an index and governing means therefor' comprising indicating and compensating expansion tubes, one tube being fixcdly mounted at one end and the other tube movably mounted and connected to the opposite end of said first tube to receive the motion thereof and also havinghan end operatively connected to said index, fluid contain-' ing systems for exposure to temperature conditions comprising pipes communicating with said tubes, one opening to the fixedly mounted end of one tube and the other opening to said movably mounted tube and being convoluted to form a flexible connection thereto permitting uiiin'ipeded movement thereof.

5. An instrument offthe class described con'iprising incombination, an index, and governing means therefor including indicating and compensating tubes, means whereby the indicating tube is moved bodily by the compensating tube, `a bulb, and a pipe connecting said bulb with said indicating tube and having provision permitting movement of said indicating tube substantially unimpeded by said pipe. 1

6. An instrui'nent-.of the class described comprising in combination, an index, and governing means therefor including indicating and compensating tubes means whereby the indicating tube is moved bodily by the compensating tube, al bulb, and a pipe connecting said bulb with said indicating tube and formed to present a flexible coil for per- Jmitting substantially unimpeded movement of said indicating tube.

7. An instrument of the class described comprising in combination, an index, and governing means therefor including indicating and compensatii'ig tubes, means 4whereby the indicating tube is moved bodily by the compensating tube, a bulb, a; pipe connecting said bulb with said indicating tube having a V,flexible coil therein, a frame supporting said tubes, and means for securing said pipe to said frame at a point between said coil and bulb.

In testimony whereof, l have signed my 

